Middle 1/3 of the Course PSYC 3040

CH-6, 8, 9, 10

Real Movement

An object is really moving

Apparent Movement

A stationary object is appearing in different positions, creating illusion of movement

Induced Movement

The movement of one object gives illusion that another object is moving

Movement after effect

When you look at something moving for a while, afterwards things will still appear to be moving

Freeze response

Because moving objects tend to capture attention more, animals developed a freeze response to not get caught

Kinetic Depth Effect

Movement of a 2D object’s shadow can change into perception of a 3D object

Reinhardt Detector

Used to detect motion

Two receptors , one is delayed, when they both reach at same time there is motion

Corollary Discharge signal

A copy of the eye movement is sent to visual cortex so it can tell when things are actually moving

Motor Signal

Signal sent to eyes to move eye muscles

Image Displacement Signal

Something is moving across the retina

What combination of Corollary Discharge and Image Displacement signal indicates motion?

Either only Corollary Discharge OR only Image Displacement, but not both

Evidence for corollary discharge theory

If we stare at stationary dot, and then move our eyes when we see afterimage, we perceive motion

What area of the visual pathway is responsive for motion detection)

Medial Temporal (MT) Cortex (also called V5)

Biological Motion

Placing lights on specific points of a person make it very easy to tell what is happening

Where is biological motion processed in the brain?

superior temporal sulcus (STS)

______ ________ is Inability to perceive a change in scene

Change Blindness

Examples of Change Blindness

Artificial Displays, Realistic Images, Mud splash, Continuity errors, change blindness

Inattentional Blindness

Failure to perceive unexpected objects.

Inattentional blindness vs Inattentional amnesia

Inattentional Blindness: failure to perceive stimulus
Inattentional amnesia: perceived stimulus but forgot

_______ moiton masks ______ motion in magic

Big; small

Where does action happen when pickpocketing/magic

It happens where the performer is not looking

We don’t mutlitask, we ______ between tasks

switch

If tasks are demanding what can be seen?

Performance dips

Which attention is called top-down attention

Endogenous attention

Which attention is called bottom-up attention?

Exogenous attention

paying attention to things that are different is called _____ attention

Exogenous

Visual salience

areas of stimuli that attract attention due to their properties

Feature search comes under which attention?

Exogenous

Which attention is known as “slow and serial”

Endogenous

which attention is “fully parallel”?

Exogenous

Conjunction and spatial search is associated with which attention?

Endogenous

Rank each search, from 1-3 with 1 being fast and 3 being slow, with the time taken to identify the object: Spatial Search; Feature Search; Conjunction Search

1. Feature Search

2. Conjunction Search

3. Spatial Search

Overt vs Covert attention

Overt: Involves looking directly at the object

Covert: attention without looking

Unattended objects are processed _______

slowly

Who’s study serves as evidence for mis-binding

Triesman & schmidt study

What happens in “preattentive stage” in the context of Feature Integration Theory

pre-attentive stage: feature of object are separated

What happens in the “Focused attention stage” in the context of Feature Integration Theory

features are bound into a coherent perception

In Dichotic listening task, people seem not to be processing the ______ stream?

ignored

What are some exceptions in the Dichotic listening task?

Hearing one’s own name, cuss words, intrusions

Shadowed and unshadowed

paying attention to things that are relevant is called _____ attention

endogenous

Unattended objects receive ________ processing

shallower

What are the 3 disorders of neglect

Hemispatial neglect, Extinction, Balint syndrome

Define Neglect

The inability to attend to or respond to stimuli in the contralesional visual field

Which side is usually neglected for people with visual neglect?

Left side

How can neglect be diagnosed?

Line cancellation task, Line bisection task, Copying pictures, objects, Drawing objects

What causes neglect?

Lesion in the right parietal lobe

Why is neglect usually on the left?

Due to the asymmetric attention in the brain.

PS: Left lobe controls attention to the right whereas right lobe controls attention to both sides.

The inability to perceive a stimulus in the presence of another is called

extinction

What causes neglect?

Lesion to right parietal lobe

Symptoms of Balin’t syndome

1. hard to reach out and touch/grab object (spatial localization ability)

2. very little eye movement, tend to stare straight

3. Behaves as if can only see one object at a time.

What causes balin’t syndrome?

Lesion to both sides of the brain.

Aperture Problem

Observation of small portion of larger stimulus can lead to misleading information about direction of movement

Corollary Aperture Problem

Corollary: activity of a single complex cell does not provide accurate information about direction of movement

What are 2 solutions to aperture problem

Convergence of signals and Feedback from Higher Areas

Various brain areas repsond to ___ - ____ after a stimulus is presented

50-150ms

we perceive moving stimuli by ______ where they will be

predicting

Brain seeing moving stimuli in the location where it expects them to be in the future is called what affect?

Flash Lag Affect

Where does color come from?

Electromagnetic Spectrum (400-700nm)

In combining colors, to get closer to white what do we do?

Add wavelengths

In combining colors, if we add wavelength which color will we get closer too?

White

In combining paints, to get closer to black what do we do?

Subtract wavelength

In combining paints, if we subtract wavelengths which paint do we get closer too?

Black

Additive color mixture

Superimposing yellow and blue gives us white

Subtractive color mixture

superimposing blue and yellow gives us green

What is color perception good for?

Identifying objects and Segment the scene

Humans can discriminate between how many colors?

200,000 to 20 million

How do we perceive color?

Trichromatic color theory and Opponent process theory of color

How many basic colors are needed to generate any possible color?

3

In a rainbow why can’t we see all the colors?

It’s because we see whatever our receptors are sensitive to

Mantis shrimp has _____ receptors

12

Can we perceive colors that do not exist in the rainbow?

Yes, the color purple

In context of Trichromatic theory of color pigments respond to what wavelength?

Short(419nm), Medium(531nm), Long (558nm)

What are Color metamers?

Metamers are colors that look the same but have a different spectrum

Where does color come from?

Light / Electromagnetic spectrum

What property of light determines its color?

Wavelength

Adding lights together get us closer to ____

white

How is combining light different than combining light?

Combining lights makes the color lighter by adding wavelengths, combining paint makes the image darker by subtracting wavelengths

T/F: Color helps in identifying objects

TRUE

Segmenting the Scene

Color helps to find things in a scene (EX: berries on a tree)

How many different colors can humans see?

20,000 - 200 million

How many basic colors are needed to generate any possible color?

3

Trichromatic Theory of Color

3 Different pigments in cone receptors, they respond to short (blue), medium (green), and long (red) wavelengths

T/F: We can perceive colors that do not exist in the rainbow

TRUE, we can see purple

Color Metamers

Colors that look the same but have a different spectrum

Monochromat

Person who only needs one wavelength to match any perceived color

perceives in grayscale

Dichromat

Person who needs only two wavelengths to match any color

Protanopia

Missing long-wavelength pigment

Red-Green Color Blind

Deuteranopia

Missing medium-wavelength pigment

Red-Green Color Blind

Tritanopia

Missing short-wavelength pigment

Blue-Yellow Color Blind

Ishihara Plate

Circle of differently colored dots used to diagnose color-blindness

Tetrachromacy

Very rare condition where someone has 4 color pigments instead of 3

Color Metamers for a trichromat are not metamers for a tetrachromat

Opponent-Process Theory

Some neurons are excitatory for Some Colors and Inhibit other colors

Three Mechanisms:
White/Black

Red/Green

Blue/Yellow

Evidence of Opponent-Process Theory

• Subjective experience

• Color afterimages

• Hue cancellation experiments

• Neurophysiological evidence

• Opponent neurons located in

retina and LGN

LGN / Cortical Color Neurons

Center-Surround Receptive Fields & Single Opponent Receptive Fields

V1 / Cortical Color Neurons

Edge & Double-O

T/F: Color is heavily dependent on context

TRUE

Color Constancy

Perception of colors as relatively constant in spite of changing light sources

Brain computes “true” color based on:

Surroundings

Memory of Object’s color

Corrections for unexpected correlations

McCollough Effect

After long exposure to colored horizontal or vertical lines, the lines appear to have the opposite color